The present invention relates to a method of writing a tracking servo signal pattern on a magnetic disc of a magnetic disc device for use in recording and reproducing information with a magnetic head along a concentric information track of a predetermined track pitch on the magnetic disc which is driven into a rotation.
For magnetic disc devices such as a hard disc device, it has been a usual practice that a tracking servo signal pattern is recorded in advance at a leading portion in each of a plurality of sectors provided by dividing a concentric information track, in order to record and reproduce information as the concentric information track having a predetermined track pitch on a magnetic disc.
FIG. 4 depicts an example of the tracking servo signal pattern. As shown, a magnetic disc rotates in a direction of an arrow 500, and a magnetic head unit, which includes a reproduction-only magnetic head 12 fixed integrally with a recording magnetic head 14, moves in a diametric direction 510 of the magnetic disc. First burst signals 81 and 82, second burst signals 91 and 92, third burst signals 101 and 102, and fourth burst signals 110, 111 and 112 having predetermined frequencies are recorded in advance as tracking servo signals in respective positions, which are separated in opposite directions with respect to each other from centerlines 131 and 132 of the information tracks along the diametric direction 510 of the magnetic disc, and are shifted from one another in a direction of the centerline 131 of the information track.
The device is so constructed that the reproduction-only head 12 reproduces each of at least two signals out of the first, second, third and fourth burst signals, when recording or reproducing information. The device then records or reproduces the information on a predetermined information track by aligning a position of the recording head 14, while controlling a position of the reproduction-only head 12 in a such manner that a ratio in level between the reproduced signals of the reproduced burst signals becomes equal to a predetermined proportion.
A consideration is given now for an example in that information is recorded on or reproduced from an information track, where the first burst signal 81 and the second burst signal 91 are positioned with respect to the centerline 131 of the information track, as shown in FIG. 4. The device reproduces the first burst signal 81 and the second burst signal 91, and controls a position of the magnetic head unit in a manner that a ratio in level of the first burst signal 81 and the second burst signal 91 becomes equal to a predetermined value, so as to obtain a normal tracking. Or, if the device records or reproduces information on another information track, where the third burst signal 102 and the fourth burst signal 111 are positioned with respect to the centerline 132 of the information track, the device obtains a normal tracking by reproducing the third burst signal 102 and the fourth burst signal 111, and controlling a position of the magnetic head unit in a manner that a ratio in reproduced signal level of the third burst signal 102 and the fourth burst signal 111 becomes equal to a predetermined value.
As a conventional method of writing the tracking servo signal pattern having the afore-noted first, second, third and fourth burst signals on a magnetic disc, a device called xe2x80x9cservo track writerxe2x80x9d designed exclusively for writing has been used. The servo track writer records the first, second, third and fourth burst signals 81, 82, 91, 92, 101, 102, 110, 111, 112 and so on by controlling a position as well as a recording and an erasing timings of a magnetic head unit provided in a magnetic disc device with a control system of the servo track writer, while rotating the magnetic disc of the magnetic disc device.
A conventional method of writing the tracking servo signal pattern using a servo track writer will be described hereinafter by referring to FIG. 5.
Firstly, the recording head 14 is aligned in a position where a burst signal 81a is to be written, and the burst signal 81a is written in. A time required for this process is the sum of an aligning time and a time for the disc to rotate for a full turn. Then, the recording head 14 is aligned in another position where a burst signal 101a is to be written, and the burst signal 101a is written in. A time required for this process is also the sum of the aligning time and the time for the disc to rotate for a full turn.
Next, the recording head 14 is aligned in a position where a burst signal 91a is to be written in the diametric direction 510 of the magnetic disc, and the burst signal 91a is written immediately after demagnetizing a portion 81b of the already written burst signal 81a. A time required for this process is also the sum of the aligning time and the time for the disc to rotate for a full turn. The recording head 14 is then aligned in a position where a burst signal 111a is to be written in the diametric direction 510 of the magnetic disc, and the burst signal 111a is written immediately after demagnetizing a portion 101b. A time required for this process is the sum of the aligning time and the time for the disc to rotate for a full turn.
Then, the recording head 14 is aligned in a position where a burst signal 82a is to be written, and a portion 91b is demagnetized immediately after writing the burst signal 82a. A time required for this process is the sum of the aligning time and the time for the disc to rotate for a full turn.
All of the burst signals are written by repeating the process described above. Hence, a time necessary for writing can be given by the following formula:
(aligning time+time for a disc to rotate for a full turn)xc3x97number of burst signals
However, a servo track writer for use in the foregoing writing method is very expensive equipment. Therefore, it is desirable for such expensive equipment to be utilized efficiently. However, it has not necessarily been utilized efficiently, since all of the first, second, third, and fourth burst signals are recorded under control of the servo track writer, as has been described.
A portion of the tracking servo signals or a special signal of the magnetic disc device is written under control of a control system of the servo track writer and writing the rest of the tracking servo signals thereafter under control of the magnetic disc device""s own control system based on the already written tracking servo signals without using the servo track writer.
Thus, method of writing a tracking servo signal pattern for a magnetic disc device in accordance with an exemplary embodiment of the present invention includes the steps of: recording a set of tracking servo signals out of a plurality of sets with a magnetic head unit equipped within the magnetic disc device under control of a control system of a writing device of tracking servo signals (xe2x80x9cservo track writerxe2x80x9d); reproducing the set of tracking servo signals with the magnetic head unit equipped in the magnetic disc device under control of a control system of the magnetic disc device by itself; and recording tracking servo signal pattern not yet recorded among the plurality of sets with the magnetic head unit equipped in the magnetic disc device, while controlling a position of the magnetic head unit under control of a control system of the magnetic disc device by itself based on the reproduced signals.
According to this method, a utilization efficiency of the servo track writer is improved by at least equal to or more than double, since the servo track writer records only one set of the tracking servo signals. Also, the invention does not necessitate any consideration, in particular, for utilization efficiency and so on of a special equipment such as the servo track writer because the tracking servo signal pattern of the other set are recorded by magnetic head units equipped in the magnetic disc devices themselves under control of the control systems of the individual magnetic disc devices themselves.
In addition, a method of writing a tracking servo signal pattern for a magnetic disc device of the present invention includes: recording a first burst signal and a second burst signal with a magnetic head unit equipped within the magnetic disc device under control of the control system of the writing device of tracking servo signals; followed thereafter by reproducing the first burst signal and the second burst signal with the magnetic head unit equipped in the magnetic disc device under control of a control system of the magnetic disc device by itself; and recording patterns of a third burst signal and a fourth burst signal with the magnetic head unit equipped in the magnetic disc device, while controlling a position of the magnetic head unit in a manner that a ratio in level of both of the reproduced signals becomes equal to a predetermined value.
According to this method, a utilization efficiency of the servo track writer is improved by at least equal to or more than double, because only the first and the second burst signals are recorded under control of the control system of the servo track writer, and patterns of the third and the fourth burst signal are recorded by the magnetic head units equipped in the magnetic disc devices themselves under control of the control systems of the individual magnetic disc devices themselves.